drivers/tty/sysrq.c

   1 /*
   2  *      Linux Magic System Request Key Hacks
   3  *
   4  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   5  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   6  *
   7  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   8  *      overhauled to use key registration
   9  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  10  *
  11  *      Copyright (c) 2010 Dmitry Torokhov
  12  *      Input handler conversion
  13  */
  14
  15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  16
  17 #include <linux/sched.h>
  18 #include <linux/sched/rt.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/mm.h>
  21 #include <linux/fs.h>
  22 #include <linux/mount.h>
  23 #include <linux/kdev_t.h>
  24 #include <linux/major.h>
  25 #include <linux/reboot.h>
  26 #include <linux/sysrq.h>
  27 #include <linux/kbd_kern.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/nmi.h>
  30 #include <linux/quotaops.h>
  31 #include <linux/perf_event.h>
  32 #include <linux/kernel.h>
  33 #include <linux/module.h>
  34 #include <linux/suspend.h>
  35 #include <linux/writeback.h>
  36 #include <linux/swap.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/vt_kern.h>
  39 #include <linux/workqueue.h>
  40 #include <linux/hrtimer.h>
  41 #include <linux/oom.h>
  42 #include <linux/slab.h>
  43 #include <linux/input.h>
  44 #include <linux/uaccess.h>
  45 #include <linux/moduleparam.h>
  46 #include <linux/jiffies.h>
  47 #include <linux/syscalls.h>
  48 #include <linux/of.h>
  49
  50 #include <asm/ptrace.h>
  51 #include <asm/irq_regs.h>
  52
  53 /* Whether we react on sysrq keys or just ignore them */
  54 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  55 static bool __read_mostly sysrq_always_enabled;
  56
  57 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };
  58 int sysrq_reset_downtime_ms __weak;
  59
  60 static bool sysrq_on(void)
  61 {
  62         return sysrq_enabled || sysrq_always_enabled;
  63 }
  64
  65 /*
  66  * A value of 1 means 'all', other nonzero values are an op mask:
  67  */
  68 static bool sysrq_on_mask(int mask)
  69 {
  70         return sysrq_always_enabled ||
  71                sysrq_enabled == 1 ||
  72                (sysrq_enabled & mask);
  73 }
  74
  75 static int __init sysrq_always_enabled_setup(char *str)
  76 {
  77         sysrq_always_enabled = true;
  78         pr_info("sysrq always enabled.\n");
  79
  80         return 1;
  81 }
  82
  83 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  84
  85
  86 static void sysrq_handle_loglevel(int key)
  87 {
  88         int i;
  89
  90         i = key - '0';
  91         console_loglevel = 7;
  92         printk("Loglevel set to %d\n", i);
  93         console_loglevel = i;
  94 }
  95 static struct sysrq_key_op sysrq_loglevel_op = {
  96         .handler        = sysrq_handle_loglevel,
  97         .help_msg       = "loglevel(0-9)",
  98         .action_msg     = "Changing Loglevel",
  99         .enable_mask    = SYSRQ_ENABLE_LOG,
 100 };
 101
 102 #ifdef CONFIG_VT
 103 static void sysrq_handle_SAK(int key)
 104 {
 105         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 106         schedule_work(SAK_work);
 107 }
 108 static struct sysrq_key_op sysrq_SAK_op = {
 109         .handler        = sysrq_handle_SAK,
 110         .help_msg       = "sak(k)",
 111         .action_msg     = "SAK",
 112         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 113 };
 114 #else
 115 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 116 #endif
 117
 118 #ifdef CONFIG_VT
 119 static void sysrq_handle_unraw(int key)
 120 {
 121         vt_reset_unicode(fg_console);
 122 }
 123
 124 static struct sysrq_key_op sysrq_unraw_op = {
 125         .handler        = sysrq_handle_unraw,
 126         .help_msg       = "unraw(r)",
 127         .action_msg     = "Keyboard mode set to system default",
 128         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 129 };
 130 #else
 131 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 132 #endif /* CONFIG_VT */
 133
 134 static void sysrq_handle_crash(int key)
 135 {
 136         char *killer = NULL;
 137
 138         panic_on_oops = 1;      /* force panic */
 139         wmb();
 140         *killer = 1;
 141 }
 142 static struct sysrq_key_op sysrq_crash_op = {
 143         .handler        = sysrq_handle_crash,
 144         .help_msg       = "crash(c)",
 145         .action_msg     = "Trigger a crash",
 146         .enable_mask    = SYSRQ_ENABLE_DUMP,
 147 };
 148
 149 static void sysrq_handle_reboot(int key)
 150 {
 151         lockdep_off();
 152         local_irq_enable();
 153         emergency_restart();
 154 }
 155 static struct sysrq_key_op sysrq_reboot_op = {
 156         .handler        = sysrq_handle_reboot,
 157         .help_msg       = "reboot(b)",
 158         .action_msg     = "Resetting",
 159         .enable_mask    = SYSRQ_ENABLE_BOOT,
 160 };
 161
 162 static void sysrq_handle_sync(int key)
 163 {
 164         emergency_sync();
 165 }
 166 static struct sysrq_key_op sysrq_sync_op = {
 167         .handler        = sysrq_handle_sync,
 168         .help_msg       = "sync(s)",
 169         .action_msg     = "Emergency Sync",
 170         .enable_mask    = SYSRQ_ENABLE_SYNC,
 171 };
 172
 173 static void sysrq_handle_show_timers(int key)
 174 {
 175         sysrq_timer_list_show();
 176 }
 177
 178 static struct sysrq_key_op sysrq_show_timers_op = {
 179         .handler        = sysrq_handle_show_timers,
 180         .help_msg       = "show-all-timers(q)",
 181         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 182 };
 183
 184 static void sysrq_handle_mountro(int key)
 185 {
 186         emergency_remount();
 187 }
 188 static struct sysrq_key_op sysrq_mountro_op = {
 189         .handler        = sysrq_handle_mountro,
 190         .help_msg       = "unmount(u)",
 191         .action_msg     = "Emergency Remount R/O",
 192         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 193 };
 194
 195 #ifdef CONFIG_LOCKDEP
 196 static void sysrq_handle_showlocks(int key)
 197 {
 198         debug_show_all_locks();
 199 }
 200
 201 static struct sysrq_key_op sysrq_showlocks_op = {
 202         .handler        = sysrq_handle_showlocks,
 203         .help_msg       = "show-all-locks(d)",
 204         .action_msg     = "Show Locks Held",
 205 };
 206 #else
 207 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 208 #endif
 209
 210 #ifdef CONFIG_SMP
 211 static DEFINE_SPINLOCK(show_lock);
 212
 213 static void showacpu(void *dummy)
 214 {
 215         unsigned long flags;
 216
 217         /* Idle CPUs have no interesting backtrace. */
 218         if (idle_cpu(smp_processor_id()))
 219                 return;
 220
 221         spin_lock_irqsave(&show_lock, flags);
 222         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 223         show_stack(NULL, NULL);
 224         spin_unlock_irqrestore(&show_lock, flags);
 225 }
 226
 227 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 228 {
 229         smp_call_function(showacpu, NULL, 0);
 230 }
 231
 232 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 233
 234 static void sysrq_handle_showallcpus(int key)
 235 {
 236         /*
 237          * Fall back to the workqueue based printing if the
 238          * backtrace printing did not succeed or the
 239          * architecture has no support for it:
 240          */
 241         if (!trigger_all_cpu_backtrace()) {
 242                 struct pt_regs *regs = get_irq_regs();
 243
 244                 if (regs) {
 245                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 246                         show_regs(regs);
 247                 }
 248                 schedule_work(&sysrq_showallcpus);
 249         }
 250 }
 251
 252 static struct sysrq_key_op sysrq_showallcpus_op = {
 253         .handler        = sysrq_handle_showallcpus,
 254         .help_msg       = "show-backtrace-all-active-cpus(l)",
 255         .action_msg     = "Show backtrace of all active CPUs",
 256         .enable_mask    = SYSRQ_ENABLE_DUMP,
 257 };
 258 #endif
 259
 260 static void sysrq_handle_showregs(int key)
 261 {
 262         struct pt_regs *regs = get_irq_regs();
 263         if (regs)
 264                 show_regs(regs);
 265         perf_event_print_debug();
 266 }
 267 static struct sysrq_key_op sysrq_showregs_op = {
 268         .handler        = sysrq_handle_showregs,
 269         .help_msg       = "show-registers(p)",
 270         .action_msg     = "Show Regs",
 271         .enable_mask    = SYSRQ_ENABLE_DUMP,
 272 };
 273
 274 static void sysrq_handle_showstate(int key)
 275 {
 276         show_state();
 277 }
 278 static struct sysrq_key_op sysrq_showstate_op = {
 279         .handler        = sysrq_handle_showstate,
 280         .help_msg       = "show-task-states(t)",
 281         .action_msg     = "Show State",
 282         .enable_mask    = SYSRQ_ENABLE_DUMP,
 283 };
 284
 285 static void sysrq_handle_showstate_blocked(int key)
 286 {
 287         show_state_filter(TASK_UNINTERRUPTIBLE);
 288 }
 289 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 290         .handler        = sysrq_handle_showstate_blocked,
 291         .help_msg       = "show-blocked-tasks(w)",
 292         .action_msg     = "Show Blocked State",
 293         .enable_mask    = SYSRQ_ENABLE_DUMP,
 294 };
 295
 296 #ifdef CONFIG_TRACING
 297 #include <linux/ftrace.h>
 298
 299 static void sysrq_ftrace_dump(int key)
 300 {
 301         ftrace_dump(DUMP_ALL);
 302 }
 303 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 304         .handler        = sysrq_ftrace_dump,
 305         .help_msg       = "dump-ftrace-buffer(z)",
 306         .action_msg     = "Dump ftrace buffer",
 307         .enable_mask    = SYSRQ_ENABLE_DUMP,
 308 };
 309 #else
 310 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 311 #endif
 312
 313 static void sysrq_handle_showmem(int key)
 314 {
 315         show_mem(0);
 316 }
 317 static struct sysrq_key_op sysrq_showmem_op = {
 318         .handler        = sysrq_handle_showmem,
 319         .help_msg       = "show-memory-usage(m)",
 320         .action_msg     = "Show Memory",
 321         .enable_mask    = SYSRQ_ENABLE_DUMP,
 322 };
 323
 324 /*
 325  * Signal sysrq helper function.  Sends a signal to all user processes.
 326  */
 327 static void send_sig_all(int sig)
 328 {
 329         struct task_struct *p;
 330
 331         read_lock(&tasklist_lock);
 332         for_each_process(p) {
 333                 if (p->flags & PF_KTHREAD)
 334                         continue;
 335                 if (is_global_init(p))
 336                         continue;
 337
 338                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 339         }
 340         read_unlock(&tasklist_lock);
 341 }
 342
 343 static void sysrq_handle_term(int key)
 344 {
 345         send_sig_all(SIGTERM);
 346         console_loglevel = 8;
 347 }
 348 static struct sysrq_key_op sysrq_term_op = {
 349         .handler        = sysrq_handle_term,
 350         .help_msg       = "terminate-all-tasks(e)",
 351         .action_msg     = "Terminate All Tasks",
 352         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 353 };
 354
 355 static void moom_callback(struct work_struct *ignored)
 356 {
 357         out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
 358                       0, NULL, true);
 359 }
 360
 361 static DECLARE_WORK(moom_work, moom_callback);
 362
 363 static void sysrq_handle_moom(int key)
 364 {
 365         schedule_work(&moom_work);
 366 }
 367 static struct sysrq_key_op sysrq_moom_op = {
 368         .handler        = sysrq_handle_moom,
 369         .help_msg       = "memory-full-oom-kill(f)",
 370         .action_msg     = "Manual OOM execution",
 371         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 372 };
 373
 374 #ifdef CONFIG_BLOCK
 375 static void sysrq_handle_thaw(int key)
 376 {
 377         emergency_thaw_all();
 378 }
 379 static struct sysrq_key_op sysrq_thaw_op = {
 380         .handler        = sysrq_handle_thaw,
 381         .help_msg       = "thaw-filesystems(j)",
 382         .action_msg     = "Emergency Thaw of all frozen filesystems",
 383         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 384 };
 385 #endif
 386
 387 static void sysrq_handle_kill(int key)
 388 {
 389         send_sig_all(SIGKILL);
 390         console_loglevel = 8;
 391 }
 392 static struct sysrq_key_op sysrq_kill_op = {
 393         .handler        = sysrq_handle_kill,
 394         .help_msg       = "kill-all-tasks(i)",
 395         .action_msg     = "Kill All Tasks",
 396         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 397 };
 398
 399 static void sysrq_handle_unrt(int key)
 400 {
 401         normalize_rt_tasks();
 402 }
 403 static struct sysrq_key_op sysrq_unrt_op = {
 404         .handler        = sysrq_handle_unrt,
 405         .help_msg       = "nice-all-RT-tasks(n)",
 406         .action_msg     = "Nice All RT Tasks",
 407         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 408 };
 409
 410 /* Key Operations table and lock */
 411 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 412
 413 static struct sysrq_key_op *sysrq_key_table[36] = {
 414         &sysrq_loglevel_op,             /* 0 */
 415         &sysrq_loglevel_op,             /* 1 */
 416         &sysrq_loglevel_op,             /* 2 */
 417         &sysrq_loglevel_op,             /* 3 */
 418         &sysrq_loglevel_op,             /* 4 */
 419         &sysrq_loglevel_op,             /* 5 */
 420         &sysrq_loglevel_op,             /* 6 */
 421         &sysrq_loglevel_op,             /* 7 */
 422         &sysrq_loglevel_op,             /* 8 */
 423         &sysrq_loglevel_op,             /* 9 */
 424
 425         /*
 426          * a: Don't use for system provided sysrqs, it is handled specially on
 427          * sparc and will never arrive.
 428          */
 429         NULL,                           /* a */
 430         &sysrq_reboot_op,               /* b */
 431         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 432         &sysrq_showlocks_op,            /* d */
 433         &sysrq_term_op,                 /* e */
 434         &sysrq_moom_op,                 /* f */
 435         /* g: May be registered for the kernel debugger */
 436         NULL,                           /* g */
 437         NULL,                           /* h - reserved for help */
 438         &sysrq_kill_op,                 /* i */
 439 #ifdef CONFIG_BLOCK
 440         &sysrq_thaw_op,                 /* j */
 441 #else
 442         NULL,                           /* j */
 443 #endif
 444         &sysrq_SAK_op,                  /* k */
 445 #ifdef CONFIG_SMP
 446         &sysrq_showallcpus_op,          /* l */
 447 #else
 448         NULL,                           /* l */
 449 #endif
 450         &sysrq_showmem_op,              /* m */
 451         &sysrq_unrt_op,                 /* n */
 452         /* o: This will often be registered as 'Off' at init time */
 453         NULL,                           /* o */
 454         &sysrq_showregs_op,             /* p */
 455         &sysrq_show_timers_op,          /* q */
 456         &sysrq_unraw_op,                /* r */
 457         &sysrq_sync_op,                 /* s */
 458         &sysrq_showstate_op,            /* t */
 459         &sysrq_mountro_op,              /* u */
 460         /* v: May be registered for frame buffer console restore */
 461         NULL,                           /* v */
 462         &sysrq_showstate_blocked_op,    /* w */
 463         /* x: May be registered on ppc/powerpc for xmon */
 464         /* x: May be registered on sparc64 for global PMU dump */
 465         NULL,                           /* x */
 466         /* y: May be registered on sparc64 for global register dump */
 467         NULL,                           /* y */
 468         &sysrq_ftrace_dump_op,          /* z */
 469 };
 470
 471 /* key2index calculation, -1 on invalid index */
 472 static int sysrq_key_table_key2index(int key)
 473 {
 474         int retval;
 475
 476         if ((key >= '0') && (key <= '9'))
 477                 retval = key - '0';
 478         else if ((key >= 'a') && (key <= 'z'))
 479                 retval = key + 10 - 'a';
 480         else
 481                 retval = -1;
 482         return retval;
 483 }
 484
 485 /*
 486  * get and put functions for the table, exposed to modules.
 487  */
 488 struct sysrq_key_op *__sysrq_get_key_op(int key)
 489 {
 490         struct sysrq_key_op *op_p = NULL;
 491         int i;
 492
 493         i = sysrq_key_table_key2index(key);
 494         if (i != -1)
 495                 op_p = sysrq_key_table[i];
 496
 497         return op_p;
 498 }
 499
 500 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 501 {
 502         int i = sysrq_key_table_key2index(key);
 503
 504         if (i != -1)
 505                 sysrq_key_table[i] = op_p;
 506 }
 507
 508 void __handle_sysrq(int key, bool check_mask)
 509 {
 510         struct sysrq_key_op *op_p;
 511         int orig_log_level;
 512         int i;
 513         unsigned long flags;
 514
 515         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 516         /*
 517          * Raise the apparent loglevel to maximum so that the sysrq header
 518          * is shown to provide the user with positive feedback.  We do not
 519          * simply emit this at KERN_EMERG as that would change message
 520          * routing in the consumers of /proc/kmsg.
 521          */
 522         orig_log_level = console_loglevel;
 523         console_loglevel = 7;
 524         printk(KERN_INFO "SysRq : ");
 525
 526         op_p = __sysrq_get_key_op(key);
 527         if (op_p) {
 528                 /*
 529                  * Should we check for enabled operations (/proc/sysrq-trigger
 530                  * should not) and is the invoked operation enabled?
 531                  */
 532                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 533                         printk("%s\n", op_p->action_msg);
 534                         console_loglevel = orig_log_level;
 535                         op_p->handler(key);
 536                 } else {
 537                         printk("This sysrq operation is disabled.\n");
 538                 }
 539         } else {
 540                 printk("HELP : ");
 541                 /* Only print the help msg once per handler */
 542                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 543                         if (sysrq_key_table[i]) {
 544                                 int j;
 545
 546                                 for (j = 0; sysrq_key_table[i] !=
 547                                                 sysrq_key_table[j]; j++)
 548                                         ;
 549                                 if (j != i)
 550                                         continue;
 551                                 printk("%s ", sysrq_key_table[i]->help_msg);
 552                         }
 553                 }
 554                 printk("\n");
 555                 console_loglevel = orig_log_level;
 556         }
 557         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 558 }
 559
 560 void handle_sysrq(int key)
 561 {
 562         if (sysrq_on())
 563                 __handle_sysrq(key, true);
 564 }
 565 EXPORT_SYMBOL(handle_sysrq);
 566
 567 #ifdef CONFIG_INPUT
 568
 569 /* Simple translation table for the SysRq keys */
 570 static const unsigned char sysrq_xlate[KEY_CNT] =
 571         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 572         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 573         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 574         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 575         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 576         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 577         "\r\000/";                                      /* 0x60 - 0x6f */
 578
 579 struct sysrq_state {
 580         struct input_handle handle;
 581         struct work_struct reinject_work;
 582         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 583         unsigned int alt;
 584         unsigned int alt_use;
 585         bool active;
 586         bool need_reinject;
 587         bool reinjecting;
 588
 589         /* reset sequence handling */
 590         bool reset_canceled;
 591         bool reset_requested;
 592         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 593         int reset_seq_len;
 594         int reset_seq_cnt;
 595         int reset_seq_version;
 596         struct timer_list keyreset_timer;
 597 };
 598
 599 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 600 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 601 static unsigned int sysrq_reset_seq_len;
 602 static unsigned int sysrq_reset_seq_version = 1;
 603
 604 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 605 {
 606         int i;
 607         unsigned short key;
 608
 609         state->reset_seq_cnt = 0;
 610
 611         for (i = 0; i < sysrq_reset_seq_len; i++) {
 612                 key = sysrq_reset_seq[i];
 613
 614                 if (key == KEY_RESERVED || key > KEY_MAX)
 615                         break;
 616
 617                 __set_bit(key, state->reset_keybit);
 618                 state->reset_seq_len++;
 619
 620                 if (test_bit(key, state->key_down))
 621                         state->reset_seq_cnt++;
 622         }
 623
 624         /* Disable reset until old keys are not released */
 625         state->reset_canceled = state->reset_seq_cnt != 0;
 626
 627         state->reset_seq_version = sysrq_reset_seq_version;
 628 }
 629
 630 static void sysrq_do_reset(unsigned long _state)
 631 {
 632         struct sysrq_state *state = (struct sysrq_state *) _state;
 633
 634         state->reset_requested = true;
 635
 636         sys_sync();
 637         kernel_restart(NULL);
 638 }
 639
 640 static void sysrq_handle_reset_request(struct sysrq_state *state)
 641 {
 642         if (state->reset_requested)
 643                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 644
 645         if (sysrq_reset_downtime_ms)
 646                 mod_timer(&state->keyreset_timer,
 647                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 648         else
 649                 sysrq_do_reset((unsigned long)state);
 650 }
 651
 652 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 653                                         unsigned int code, int value)
 654 {
 655         if (!test_bit(code, state->reset_keybit)) {
 656                 /*
 657                  * Pressing any key _not_ in reset sequence cancels
 658                  * the reset sequence.  Also cancelling the timer in
 659                  * case additional keys were pressed after a reset
 660                  * has been requested.
 661                  */
 662                 if (value && state->reset_seq_cnt) {
 663                         state->reset_canceled = true;
 664                         del_timer(&state->keyreset_timer);
 665                 }
 666         } else if (value == 0) {
 667                 /*
 668                  * Key release - all keys in the reset sequence need
 669                  * to be pressed and held for the reset timeout
 670                  * to hold.
 671                  */
 672                 del_timer(&state->keyreset_timer);
 673
 674                 if (--state->reset_seq_cnt == 0)
 675                         state->reset_canceled = false;
 676         } else if (value == 1) {
 677                 /* key press, not autorepeat */
 678                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 679                     !state->reset_canceled) {
 680                         sysrq_handle_reset_request(state);
 681                 }
 682         }
 683 }
 684
 685 #ifdef CONFIG_OF
 686 static void sysrq_of_get_keyreset_config(void)
 687 {
 688         u32 key;
 689         struct device_node *np;
 690         struct property *prop;
 691         const __be32 *p;
 692
 693         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 694         if (!np) {
 695                 pr_debug("No sysrq node found");
 696                 return;
 697         }
 698
 699         /* Reset in case a __weak definition was present */
 700         sysrq_reset_seq_len = 0;
 701
 702         of_property_for_each_u32(np, "keyset", prop, p, key) {
 703                 if (key == KEY_RESERVED || key > KEY_MAX ||
 704                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 705                         break;
 706
 707                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 708         }
 709
 710         /* Get reset timeout if any. */
 711         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 712 }
 713 #else
 714 static void sysrq_of_get_keyreset_config(void)
 715 {
 716 }
 717 #endif
 718
 719 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 720 {
 721         struct sysrq_state *sysrq =
 722                         container_of(work, struct sysrq_state, reinject_work);
 723         struct input_handle *handle = &sysrq->handle;
 724         unsigned int alt_code = sysrq->alt_use;
 725
 726         if (sysrq->need_reinject) {
 727                 /* we do not want the assignment to be reordered */
 728                 sysrq->reinjecting = true;
 729                 mb();
 730
 731                 /* Simulate press and release of Alt + SysRq */
 732                 input_inject_event(handle, EV_KEY, alt_code, 1);
 733                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 734                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 735
 736                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 737                 input_inject_event(handle, EV_KEY, alt_code, 0);
 738                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 739
 740                 mb();
 741                 sysrq->reinjecting = false;
 742         }
 743 }
 744
 745 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 746                                   unsigned int code, int value)
 747 {
 748         bool was_active = sysrq->active;
 749         bool suppress;
 750
 751         switch (code) {
 752
 753         case KEY_LEFTALT:
 754         case KEY_RIGHTALT:
 755                 if (!value) {
 756                         /* One of ALTs is being released */
 757                         if (sysrq->active && code == sysrq->alt_use)
 758                                 sysrq->active = false;
 759
 760                         sysrq->alt = KEY_RESERVED;
 761
 762                 } else if (value != 2) {
 763                         sysrq->alt = code;
 764                         sysrq->need_reinject = false;
 765                 }
 766                 break;
 767
 768         case KEY_SYSRQ:
 769                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 770                         sysrq->active = true;
 771                         sysrq->alt_use = sysrq->alt;
 772                         /*
 773                          * If nothing else will be pressed we'll need
 774                          * to re-inject Alt-SysRq keysroke.
 775                          */
 776                         sysrq->need_reinject = true;
 777                 }
 778
 779                 /*
 780                  * Pretend that sysrq was never pressed at all. This
 781                  * is needed to properly handle KGDB which will try
 782                  * to release all keys after exiting debugger. If we
 783                  * do not clear key bit it KGDB will end up sending
 784                  * release events for Alt and SysRq, potentially
 785                  * triggering print screen function.
 786                  */
 787                 if (sysrq->active)
 788                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 789
 790                 break;
 791
 792         default:
 793                 if (sysrq->active && value && value != 2) {
 794                         sysrq->need_reinject = false;
 795                         __handle_sysrq(sysrq_xlate[code], true);
 796                 }
 797                 break;
 798         }
 799
 800         suppress = sysrq->active;
 801
 802         if (!sysrq->active) {
 803
 804                 /*
 805                  * See if reset sequence has changed since the last time.
 806                  */
 807                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 808                         sysrq_parse_reset_sequence(sysrq);
 809
 810                 /*
 811                  * If we are not suppressing key presses keep track of
 812                  * keyboard state so we can release keys that have been
 813                  * pressed before entering SysRq mode.
 814                  */
 815                 if (value)
 816                         set_bit(code, sysrq->key_down);
 817                 else
 818                         clear_bit(code, sysrq->key_down);
 819
 820                 if (was_active)
 821                         schedule_work(&sysrq->reinject_work);
 822
 823                 /* Check for reset sequence */
 824                 sysrq_detect_reset_sequence(sysrq, code, value);
 825
 826         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 827                 /*
 828                  * Pass on release events for keys that was pressed before
 829                  * entering SysRq mode.
 830                  */
 831                 suppress = false;
 832         }
 833
 834         return suppress;
 835 }
 836
 837 static bool sysrq_filter(struct input_handle *handle,
 838                          unsigned int type, unsigned int code, int value)
 839 {
 840         struct sysrq_state *sysrq = handle->private;
 841         bool suppress;
 842
 843         /*
 844          * Do not filter anything if we are in the process of re-injecting
 845          * Alt+SysRq combination.
 846          */
 847         if (sysrq->reinjecting)
 848                 return false;
 849
 850         switch (type) {
 851
 852         case EV_SYN:
 853                 suppress = false;
 854                 break;
 855
 856         case EV_KEY:
 857                 suppress = sysrq_handle_keypress(sysrq, code, value);
 858                 break;
 859
 860         default:
 861                 suppress = sysrq->active;
 862                 break;
 863         }
 864
 865         return suppress;
 866 }
 867
 868 static int sysrq_connect(struct input_handler *handler,
 869                          struct input_dev *dev,
 870                          const struct input_device_id *id)
 871 {
 872         struct sysrq_state *sysrq;
 873         int error;
 874
 875         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 876         if (!sysrq)
 877                 return -ENOMEM;
 878
 879         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 880
 881         sysrq->handle.dev = dev;
 882         sysrq->handle.handler = handler;
 883         sysrq->handle.name = "sysrq";
 884         sysrq->handle.private = sysrq;
 885         setup_timer(&sysrq->keyreset_timer,
 886                     sysrq_do_reset, (unsigned long)sysrq);
 887
 888         error = input_register_handle(&sysrq->handle);
 889         if (error) {
 890                 pr_err("Failed to register input sysrq handler, error %d\n",
 891                         error);
 892                 goto err_free;
 893         }
 894
 895         error = input_open_device(&sysrq->handle);
 896         if (error) {
 897                 pr_err("Failed to open input device, error %d\n", error);
 898                 goto err_unregister;
 899         }
 900
 901         return 0;
 902
 903  err_unregister:
 904         input_unregister_handle(&sysrq->handle);
 905  err_free:
 906         kfree(sysrq);
 907         return error;
 908 }
 909
 910 static void sysrq_disconnect(struct input_handle *handle)
 911 {
 912         struct sysrq_state *sysrq = handle->private;
 913
 914         input_close_device(handle);
 915         cancel_work_sync(&sysrq->reinject_work);
 916         del_timer_sync(&sysrq->keyreset_timer);
 917         input_unregister_handle(handle);
 918         kfree(sysrq);
 919 }
 920
 921 /*
 922  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 923  * keyboards have SysRq key predefined and so user may add it to keymap
 924  * later, but we expect all such keyboards to have left alt.
 925  */
 926 static const struct input_device_id sysrq_ids[] = {
 927         {
 928                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 929                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 930                 .evbit = { BIT_MASK(EV_KEY) },
 931                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 932         },
 933         { },
 934 };
 935
 936 static struct input_handler sysrq_handler = {
 937         .filter         = sysrq_filter,
 938         .connect        = sysrq_connect,
 939         .disconnect     = sysrq_disconnect,
 940         .name           = "sysrq",
 941         .id_table       = sysrq_ids,
 942 };
 943
 944 static bool sysrq_handler_registered;
 945
 946 static inline void sysrq_register_handler(void)
 947 {
 948         unsigned short key;
 949         int error;
 950         int i;
 951
 952         /* First check if a __weak interface was instantiated. */
 953         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 954                 key = platform_sysrq_reset_seq[i];
 955                 if (key == KEY_RESERVED || key > KEY_MAX)
 956                         break;
 957
 958                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 959         }
 960
 961         /*
 962          * DT configuration takes precedence over anything that would
 963          * have been defined via the __weak interface.
 964          */
 965         sysrq_of_get_keyreset_config();
 966
 967         error = input_register_handler(&sysrq_handler);
 968         if (error)
 969                 pr_err("Failed to register input handler, error %d", error);
 970         else
 971                 sysrq_handler_registered = true;
 972 }
 973
 974 static inline void sysrq_unregister_handler(void)
 975 {
 976         if (sysrq_handler_registered) {
 977                 input_unregister_handler(&sysrq_handler);
 978                 sysrq_handler_registered = false;
 979         }
 980 }
 981
 982 static int sysrq_reset_seq_param_set(const char *buffer,
 983                                      const struct kernel_param *kp)
 984 {
 985         unsigned long val;
 986         int error;
 987
 988         error = kstrtoul(buffer, 0, &val);
 989         if (error < 0)
 990                 return error;
 991
 992         if (val > KEY_MAX)
 993                 return -EINVAL;
 994
 995         *((unsigned short *)kp->arg) = val;
 996         sysrq_reset_seq_version++;
 997
 998         return 0;
 999 }
1000
1001 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
1002         .get    = param_get_ushort,
1003         .set    = sysrq_reset_seq_param_set,
1004 };
1005
1006 #define param_check_sysrq_reset_seq(name, p)    \
1007         __param_check(name, p, unsigned short)
1008
1009 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1010                          &sysrq_reset_seq_len, 0644);
1011
1012 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1013
1014 #else
1015
1016 static inline void sysrq_register_handler(void)
1017 {
1018 }
1019
1020 static inline void sysrq_unregister_handler(void)
1021 {
1022 }
1023
1024 #endif /* CONFIG_INPUT */
1025
1026 int sysrq_toggle_support(int enable_mask)
1027 {
1028         bool was_enabled = sysrq_on();
1029
1030         sysrq_enabled = enable_mask;
1031
1032         if (was_enabled != sysrq_on()) {
1033                 if (sysrq_on())
1034                         sysrq_register_handler();
1035                 else
1036                         sysrq_unregister_handler();
1037         }
1038
1039         return 0;
1040 }
1041
1042 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1043                                 struct sysrq_key_op *remove_op_p)
1044 {
1045         int retval;
1046         unsigned long flags;
1047
1048         spin_lock_irqsave(&sysrq_key_table_lock, flags);
1049         if (__sysrq_get_key_op(key) == remove_op_p) {
1050                 __sysrq_put_key_op(key, insert_op_p);
1051                 retval = 0;
1052         } else {
1053                 retval = -1;
1054         }
1055         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
1056         return retval;
1057 }
1058
1059 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1060 {
1061         return __sysrq_swap_key_ops(key, op_p, NULL);
1062 }
1063 EXPORT_SYMBOL(register_sysrq_key);
1064
1065 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1066 {
1067         return __sysrq_swap_key_ops(key, NULL, op_p);
1068 }
1069 EXPORT_SYMBOL(unregister_sysrq_key);
1070
1071 #ifdef CONFIG_PROC_FS
1072 /*
1073  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1074  */
1075 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1076                                    size_t count, loff_t *ppos)
1077 {
1078         if (count) {
1079                 char c;
1080
1081                 if (get_user(c, buf))
1082                         return -EFAULT;
1083                 __handle_sysrq(c, false);
1084         }
1085
1086         return count;
1087 }
1088
1089 static const struct file_operations proc_sysrq_trigger_operations = {
1090         .write          = write_sysrq_trigger,
1091         .llseek         = noop_llseek,
1092 };
1093
1094 static void sysrq_init_procfs(void)
1095 {
1096         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1097                          &proc_sysrq_trigger_operations))
1098                 pr_err("Failed to register proc interface\n");
1099 }
1100
1101 #else
1102
1103 static inline void sysrq_init_procfs(void)
1104 {
1105 }
1106
1107 #endif /* CONFIG_PROC_FS */
1108
1109 static int __init sysrq_init(void)
1110 {
1111         sysrq_init_procfs();
1112
1113         if (sysrq_on())
1114                 sysrq_register_handler();
1115
1116         return 0;
1117 }
1118 module_init(sysrq_init);